Sandy I. Helman

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Prostaglandins are important in signaling pathways involved in modulating the rates of Na+ transport in a diverse group of tissues possessing apical membrane epithelial channels. PGE2 is known to cause either stimulation, inhibition or transient stimulatory changes of Na+ transport. We have continued our studies of frog skins that are known to respond to(More)
Aldosterone, a steroid hormone, regulates renal Na+ reabsorption and, therefore, plays an important role in the maintenance of salt and water balance. In a model renal epithelial cell line (A6) we have found that phosphoinositide 3-kinase (PI 3-kinase) activity is required for aldosterone-stimulated Na+ reabsorption. Inhibition of PI 3-kinase by the(More)
Blocker-induced noise analysis of apical membrane Na channels of epithelia of frog skin was carried out with the electroneutral blocker (CDPC, 6-chloro-3,5-diamino-pyrazine-2-carboxamide) that permitted determination of the changes of single-channel Na currents and channel densities with minimal inhibition of the macroscopic rates of Na transport(More)
HELMAN, S. I., J. J. GRANTHAM, AND M. B. BURG. Eject of vasopressin on electrical resistance of renal cortical collecting tubules. Am. J. Physiol. 220(6) : 1825-1832. 197 1 .-A method is reported for measuring the transepithelial potential difference and electrical resistance in isolated rabbit renal cortical collecting tubules. The mean resistance with(More)
To study the mechanisms by which antidiuretic hormone and prostaglandins regulate Na transport at the apical membranes of the cells of anuran tissues, studies were done with fluctuation analysis. Epithelia of frog skin (Rana pipiens) were treated with vasopressin alone, or treated with vasopressin after inhibition of Na transport by indomethacin. The(More)
Noise analysis of the Na+ channels of the apical membranes of frog skin bathed symmetrically in a Cl-HCO3 Ringer solution was done with amiloride and CGS 4270. Tissues were studied in their control states and after inhibition of transepithelial Na+ transport (Isc) by addition of quinine or quinidine to the apical solution. A critical examination of the(More)
To evaluate possible mechanisms of transport at apical and basolateral barriers of Na transporting cells of epithelia, it is necessary to know the difference of electrochemical potentials at each barrier. A reevaluation in light of new data of intracellular voltages of frog skin leads to fundamental questions concerning the origin of the voltages at both(More)
Although a variety of hormones and other agents modulate renal Na+ transport acting by way of the epithelial Na+ channel (ENaC), the mode(s), pathways, and their interrelationships in regulation of the channel remain largely unknown. It is likely that several hormones may be present concurrently in vivo, and it is, therefore, important to understand(More)
Impedance analysis of the isolated epithelium of frog skin (northern Rana pipiens) was carried out in the frequency range between 0.1 Hz and 5.5 kHz while Na+ transport was abolished. Under these conditions, the impedance is determined almost completely by the dielectric properties of the apical membranes of the cells and the parallel shunt resistance. The(More)